Display devices using liquid crystal compounds are widely used at the present time and are usually driven by TN (twisted nematic) mode.
When driving by TN mode is adopted, however, the positions of liquid crystal compound molecules in an element of the device must be altered in order to change a displayed image. As a result, there are involved such problems that time required for driving the device is prolonged, and the voltage required for altering positions of the liquid crystal compound molecules, i.e., power consumption, becomes large.
Switching elements incorporating ferroelectric or antiferroelectric liquid crystal compounds, different from those in which TN mode or STN mode is utilized, can function only by altering the molecular orientation direction of the liquid crystal compounds, and therefore the switching time is prominently shortened. Further, the value Ps.times.E given from a spontaneous polarization (Ps) of the ferroelectric or antiferroelectric liquid crystal compound and an intensity of the electric field (E) applied is an effective energy output for altering the molecular orientation direction of the liquid crystal compound, and therefore the power consumption is also significantly diminished. The ferroelectric liquid crystal compounds have two stable states, namely, bistability, and the antiferroelectric liquid crystal compounds have three stable states, in accordance with the direction of the applied electric field. Consequently, they show very excellent switching threshold value characteristics and are particularly suitable for display devices for animation.
When these ferroelectric or antiferroelectric liquid crystal compounds are used in optical switching elements, etc., they are required to have various characteristics such as an operating temperature in the vicinity of or not higher than room temperature, a wide operating temperature range, a high (quick) switching speed, and a switching threshold value voltage in an appropriate range. Of these characteristics, the operating temperature range is a particularly important property when the ferroelectric or antiferroelectric liquid crystal compounds are put into practical use.
So far as ferroelectric or antiferroelectric liquid crystal compounds known hitherto are concerned, however, they have such drawbacks that the operating temperature range is generally narrow; the operating temperature range is in a high temperature region not including room temperature even when their operating temperature range is wide; and the switching speed at room temperature is low (slow). Thus, the ferroelectric or antiferroelectric liquid crystal compounds are desired to be further improved.
The present invention is intended to solve such problems associated with the prior art as described above, and it is an object of the invention to provide a novel polycyclic compound capable of becoming a liquid crystal material having excellent characteristics, a liquid crystal material consisting of the polycyclic compound, a liquid crystal composition comprising the liquid crystal material, and a liquid crystal element.